Such drawer slides are typically known as precision drawer slides. The applications for such drawer slides include loads and drawer sizes that are considered to be among the most severe and substantial in the drawer slide industry. In order to insure that drawer slide capacity is adequate, the multiple channel members are used to distribute the vertical loading evenly while providing a smooth opening and closing operation. For example, three channel members may be used. The channel members include a cabinet channel, a center channel and a drawer channel. The channels are engaged to operate in a telescoping fashion. While the conventional precision slide of this type employs three channel members, it is not inconceivable that more than three members could be used.
The functional movement of the drawer slide is designed to facilitate the opening and closing of a drawer within a cabinet structure. The telescoping action of this type of drawer slide accomplishes the opening and closing function smoothly and with little effort. As may be appreciated, the opening function terminates when the telescoping elements of the drawer slide reach the end, or termination point, of their travel. This termination point is determined by components of the drawer slide which are not subject of the present invention, but which are collectively known as "out-stop" features. The "out-stop" features in such drawer slides stop the forward progress of the slide at a predetermined point, which usually occurs when the drawer is fully open.
The reverse situation occurs when the drawer is closed and the slide is returned to a fully retracted position, wherein the channels are in substantial alignment with each other. This is known as the "in-stop" function, and is somewhat similar to the out-stop function, in that drawer travel to the retracted position is halted at a preselected point. However, the considerations for "in-stop" protection are somewhat different than for "out-stop" protection. The objective for in-stop protection is to prevent damage from occurring between the drawer front and the cabinet face or frame. In-stop features allow the drawer to be stopped, by acting through the elements of the drawer slide itself, which transfers the stopping force to the frame or side walls of the cabinet.
Drawer slides are known which utilize an in-stop feature positioned toward the rear of the installed cabinet member. Typically, these well-known in-stop designs comprise a metal tab which is turned upwardly into the center part of the channel area so as to form a positive obstruction to the travel of the center channel thereby preventing it from traveling into the cabinet enclosure after the center channel contacts the obstruction. Refinements on this approach have occurred primarily in the area of providing a resilient covering around the metal tab so as to lessen the impact on the center channel.
The in-stop function may also include a rear mounted stop on the center channel, again comprising tabs that can be folded into position to obstruct travel of the drawer member. In this fashion, the combination of stops on both the center channel and the cabinet channel work in cooperation to provide a positive in-stop feature that approximates the desired closed positioning of the drawer within the cabinet frame. However, this approach has deficiencies.
The problems which have plagued the in-stops of the prior art result from both the location and the construction of the in-stop components. Specifically, the metal tab, which is turned 90.degree. to provide obstruction to travel of an adjacent channel, is subject to deformation where extreme closing force is generated when a drawer is closed quickly, as would be the case in a fully loaded drawer. The in-stop devices taught by the prior art may be inelastically deformed, thereby changing the stopping position of the drawer slide. In addition, placement of the in-stop elements at the rear portion of the slide increases the potential for error in setting the actual stopping point of the drawer. For example, in a drawer slide with a cabinet channel length of 18 inches, the in-stop components of the drawer slide are located close to 18 inches away from the front of the cabinet and the drawer face. Imperfections in manufacturing or materials introduce tolerance factors which can materially affect the accuracy of the stopping position of the drawer from cabinet to cabinet.
There are other drawer slide configurations that differ from the three channel telescoping product described above. For example, there are two channel member slides with in-stop functions similar to those described above. It should therefore be appreciated that the teachings of the present invention are applicable to drawer slides employing two channel members or more, wherever a compatible telescoping operation of channels is found.